Pressure-and temperature-controlled apparatus for large-scale production of crystals by the czochralski technique

ABSTRACT

Furnace assembly providing a working volume the pressure in which may range from 10 5 torr to 135 atmospheres. Controlled temperatures up to 3,000*C are attainable. A crystal-pulling rod and a crucible-supporting rod extend into the furnace. The crystal-pulling rod is rotated and driven translationally through an extended excursion in a slow crystal-pulling mode and relatively fast positioning mode; while the crucible support rod is rotated and driven translationally through a relatively short excursion in a crucible positioning mode. The main furnace housing is lifted up and swung away to permit ready access to the crucible holding zone for interchange of rf coils and crucible holders as well as for easy safe removal of large crystals suspended from the pulling rod. Means are provided continuously to indicate the precise position of the crystal-pulling rod, to monitor the operation within the furnace by TV, and to control the operations within the furnace from a remote location.

Unite States Patent [191 Wenckus et al.

[ Feb. 11, 1975 1 PRESSURE-AND TEMPERATURE-CONTROLLED APPARATUS FORLARGE-SCALE PRODUCTION OF CRYSTALS BY THE CZOCHRALSKI TECHNIQUE [75]Inventors: Joseph F. Wenckus, Needham;

Roger A. Castonguay, Salem; Bernard C. Hanfly, Chestnut Hill; Francis J.Mallahan, Woburn, all of Mass.

[73] Assignee: Arthur D. Little, Inc., Cambridge,

Mass.

[22] Filed: Sept. 23, 1971 21 Appl. No.: 183,169

[52] US. Cl. 23/273 SP, 23/301 SP [51] Int. Cl B01j 17/18 [58] Field ofSearch 23/273 SP, 301 SP [56] References Cited UNITED STATES PATENTS3,002,320 10/1961 Theuerer 23/273 3,337,303 8/1967 Lorenzini 23/2733,353,914 11/1967 Pickar, Jr 23/273 3,372,003 3/1968 Yamase 23/2733,493,770 2/1970 Dessauer et a1. 23/273 3,501,406 3/1970 Kappelmeyer eta1. 23/301 SP l/l97l 3/1972 Dohcrty et al 4. 23/273 3,650,701 Forrat23/273 [57] ABSTRACT Furnace assembly providing a working volume thepressure in which may range from 10 torr to 135 atmospheres. Controlledtemperatures up to 3,000C are attainable. A crystal-pulling rod and acruciblesupporting rod extend into the furnace. The crystalpulling rodis rotated and driven translationally through an extended excursion in aslow crystalpulling mode and relatively fast positioning mode; while thecrucible support rod is rotated and driven translationally through arelatively short excursion in a crucible positioning mode. The mainfurnace housing is lifted up and swung away to permit ready access tothe crucible holding zone for interchange of rf coils and crucibleholders as well as for easy safe removal of large crystals suspendedfrom the pulling rod. Means are provided continuously to indicate theprecise position of the crystal-pulling rod, to monitor the operationwithin the furnace by TV, and to control the operations within thefurnace from a remote location.

12 Claims, 23 Drawing Figures PMEFJTED 1 SHEET O20F 18 //vVE/V7'0/?$Roger A. Costonguuy Bernard C. Henley Francis J. Mollohon v Joseph F.Wenckus /i""" a 7 l( Fig. 2

PATENTED 75 SHEET Cu 0F 18 //V|/E/VTOR.S

Roger A. Costonguuy Bernard C. Honley Froncis.J. Mulluhon Hyv Joseph F.Wenckus Attorney PMENTEUFEBI 11% 3 865,554

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m'EmEu Em 1 I975 3; 865,554 sum as ur 18 //V VENTOl-TS Roger ACustonguoy Bernard C. Henley Francis J. Mollahun Joseph E Wenckus Pmmnin3,865,554

SHEEI 1UUF18 I/VVE/VTORS Roger A. Ccstonguoy Bernard C. Honley FrancisJ. Mullchcln Joseph F wenckus Attorney sum 110F 18 PATENTED FEB '1 I975z 2 ul -W a .n Z a l 2 m A a MUI I INVENTORS R A. Custonquoy B rd C.Hcml e y Francis J. Mollohdn Joseph F. Wonckus I Zflorney PATENTEDFEBI 1I375 SHEET 13UF 18 Roger A Cosfo Bernard C. Hanl Francis J Mallahan BYJoseph F. Wenkus PATENTEU 1 3, 865,554

' SHEET 150F153 M VEA/TORS Roger A Casfonguuy Bernard C. Henley FrancisJ. Mollahan Joseph F. Wenckus PIIIEIIIIII 1 I915 3,865,554

SHEET 170F 18 REVERSIBLE ELECTRO I MAGNETIC COUNTER 41e TRANSLA-,

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AC' II INPUT l 423 422 PROPORTIONAL EST E MAGNETIC 4 TEMPERATURE REACTORAMPLIFIER CONTROL SYSTEM 1 VOLTS INDUCTION SIGNAL HEATING 7 POWER 42ISUPPLY RADIAMATIC PYROMETER PYRoMETER INVENTO/RS Lad/ Tforney PMEHIEB EB3,865,554

SHEET 18UF18 76 55 0c MOTOR CQNTROL I f T 43| AC E;\

75 1 5 AC 69 68 5| 1 l 222 74 DC I MOTOR CO'NTROL AC 432 H I DC MOTORCONTROL I D c T CLUTCH AC X POWER l 9 433 SUPPLY DC \4 MOTOR 3o CONTROLT t I /A/VEA/T0/?S AC Roger A. Costonguuy Bernard C. Hunley Francis J.Mullohun By Joseph F Wenckus PRESSURE-AND TEMPERATURE-CONTROLLEDAPPARATUS FOR LARGE-SCALE PRODUCTION OF CRYSTALS BY THE CZOCHRALSKITECHNIQUE This invention relates to an apparatus for growing crystalsand more particularly to an apparatus for growing crystals on a largescale by the Czochralski tech nique under controlled atmosphericpressures from torr to 135 atmospheres and at temperatures up to 3,000C.

An apparatus suitable for growing many different types of crystals bythe Czochralski technique is required to be able to furnish manydifferent controlled conditions. For example, the growing of crystals ofa III-V intermetallic compound may require that a very high pressure bemaintained around the growing crystal area to control the vaporizationof a volatile component such as arsenic or phosphorus in forming anintermetallic arsenide or phosphide. In other crystal growing processesit may be necessary to supply a moderate to high vacuum. In all cases,however, the working zone within the apparatus must be evacuatable topermit control of the zone atmosphere, whether it is pressurized orevacuated during crystal growth. Such a crystal growing apparatus shouldbe capable of growing crystals of oxides, salts, metals, elemental andintermetallic compound semiconductors including the phosphides,arsenides, tellurides, selenides and sulfides and any other inorganicelement, compound or mixtures thereof.

With the ever-increasing demand for single crystal raw stock for makingsemi-conductor devices, lightemitting diodes, etc., there has arisen theneed for a crystal growing apparatus which is safe, reliable and easy tooperate for the production of crystals on a large, commercial scale. Oneof the most widely accepted techniques for forming single crystals isthe vertical pulling or Czochralski technique in which a seed crystal iscontacted with the surface of a molten reservoir of the material to beformed into a crystal and then gradually pulled upwardly with rotation.

In a copending application Ser. No. 46,096 filed June I5, 1970, in ournames and assigned to the same assignee as the present application andnow U.S. Pat. No. 3,639,7 l 8, we have described and claimed amultipurpose furnace for experimental purposes for growing crystals byeither the Czochralski, Bridgman- Stockbarger, or floating-zonetechniques; for forming intermetallic compounds within controlledatmospheres such as by the methods described in U.S. Pat. No. 3,704,093and Ser. No. 169,315 filed in the names of Wilson P. Menashi, Joseph F.Wenckus and Roger A. Castonguay; and for forming doped crystals ofuniform composition. All of the above-identified applications have beenassigned to the same assignee as the present case. Inasmuch as thefurnace of Ser. No. 46.096 as a versatile research tool must provide fora wide variety of operational conditions, it is not suitable for growinglarge-scale crystals by a single technique on a commercial basis. Inaddition to providing for a wide range of operational pressures andtemperatures, a crystal growing furance suitable for growing largecrystals on a commercial basis should provide easy access for theinstallation of various sizes and types of crucibles and for the removalof large crystals, fail-safe operational features and complete remotecontrol. The

crystal growing apparatus of this invention, hereinafter eferred to as afurnace meets all of these requirements as will be evident from thefollowing detailed description.

It is therefore a primary object of this invention to provide a crystalgrowing furnace for producing crystals on a commercial scale by theCzochralski technique which may be used over a pressure range from aslow as I0 torr to as high as atmospheres and at temperatures up to3,000C. It is another object of this invention to provide apparatus ofthe character described which offers rapid. easy and safe access to theworking zone, which makes possible the growing of a crystal over a widesize range, and which permits the use of a wide variation in cruciblesizes and configurations to supply the molten crystalforming material.It is yet another object of this invention to provide such apparatuswhich is suitable for operation by remote control and remoteobservation, and which has built into it safety features which make theapparatus reliable to use under any extreme high vacuum or pressure andtemperatures desired. It is yet another object of this invention toprovide such an apparatus which permits rapid height adjustments of theupper or crystalpulling rod before, during, and after the crystalgrowing operation and which provides means for continous monitoring ofthe position of the crystal-pulling rod. Other objects of the inventionwill in part be obvious and will in part be apparent hereinafter.

The invention accordingly comprises the features of construction,combinations of elements, and arrange ments of parts which will beexemplified in the constructions hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings in which FIG. 1 is aperspective view of the apparatus of this invention showing the furnaceassembly in operational condition, the power supply and the operationalconsole;

FIG. 2 is a front view of the furnace assembly of FIG. I illustratingthe main furnace housing raised and swung away for access to the workingzone;

FIGS. 3, 4 and 5 are side, top and end views, respectively, of thecrystal-pulling rod driving mechanism;

FIG. 6 is a top plan view of the furnace assembly;

FIG. 7 is a side elevational view of the furnace assem- FIGS. 8 and 9are cross sections through the furnace chamber lift support structuretaken along lines 8-8 and 9-9, respectively, of FIG. 7;

FIG. 10 is a side elevational view of the crucible support mechansim,vacuum system, pressure-control system and hydraulic system of thefurnace assembly FIG. 11 is a front elevational view of the furnace;

FIG. 12 is a fragmentary detail of a warning device mounted on thefurance housing to prevent opening of the furnace when it ispressurized;

FIG. 13 is a front elevational view of the crucible support mechanism,vacuum system, pressure-control system and hydraulic system of thefurnace assembly;

FIG. I4 is a vertical cross section of the furnace showing one window incross section and one embodiment of the crucible holder;

1. A PRESSURE- AND TEMPERATURE-CONTROLLED APPARATUS ADAPTED FOR GROWINGCRYSTALS BY THE CZOCHRALSKI TECHNIQUE, COMPRISING IN COMBINATION A.PRESSURE-TIGHT FURNACE MEANS PROVIDING AN ENCLOSURE DIFINING THEREIN AWORKING VOLUME THE ATMOSPHERE OF WHICH MAY BE VARIED WITH RESPECT TOTEMPERATURE AND TO PRESSURE FROM A VACUUM TO AT LEAST 100 ATMOSPHERES,SAID FURNACE MEANS BEING FORMED OF A MAIN CYLINDRICAL FURNACE HOUSING OFESSENTIALLY CONSTANT DIAMETER THROUGHOUT HAVING A TOP SECTION AND BOTTOMFLANGE MEANS AND A FURNACE BASE MEMBER HAVING THE SAME INSIDE DIAMETERAS SAID MAIN FURNACE HOUSING AND BEING SEALABLE WITH SAID MAIN FURMACEHOUSING THROUGH MATING FLANGE MEANS TO LIMIT SAID ATMOSPHERE ESSENTIALLYTO SAID VOLUME; B. FURNACE SEALING MEANS ENGAGEABLE WITH SAID MATINGFLANGE MEANS AND COMPRISING TWO SEMICIRCULAR, INTERNALLY GROOVED MEMBERSAND BOLT MEANS ADAPTED TO LOCK SAID GROOVED MEMBERS IN ENGAGED POSITIONAROUND SAID MATING FLANGE MEANS; C. CRYSTAL-PULLING ROD MEANS EXTENDINGFROM EXTERNAL OF SAID MAIN FURNACE HOUSING INTO SAID VOLUME AND MOVABLETHEREIN IN BOTH ROTATIONAL AND TRANSLATIONAL MODES D. CRYSTAL-PULLINGROD BEARING AND SEALING ASSEMBLY MEANS LOCATED IN SAID TOP SECTION OFSAID MAIN FURNACE HOUSING AND PROVIDING THE SOLE SEALING MEANS BETWEENSAID CRYSTAL-PULLING ROD MEANS AND SAID PRESSURE-TIGHT FURNACE MEANS; E.ROTATIONAL AND TRANSLATION CRYSTAL-PULLING ROD DRIVING MEANS LOCATEDEXTERNAL OF SAID PRESSURE-TIGHT FURNACE MEANS AND RIGIDLY MOUNTED ONSAID MAIN FURNACE HOUSING, SAID TRANSLATIONAL DRIVING MEANS INCLUDINGMEANS TO SELECTIVELY DRIVE SAID RODS IN A SLOW CRYSTAL-GROWING MODE ORIN A RIPID-POSITIONING MODE;
 2. An apparatus according to claim 1wherein said pressure-tight furnace means includes external coolingmeans in the form of coils adapted to circulate a fluid coolant.
 3. Anapparatus according to claim 1 wherein said pressure-tight furnace meanshas associated therewith a self-resetting pressure-relief valve and asolenoid-actuated relief valve.
 4. An apparatus according to claim 1wherein said pressure-tight furnace means includes audible pressurewarning means associated with and actuated by said furnace sealingmeans.
 5. An apparatus according to claim 1 wherein said crystal-pullingrod means incorporates fluid channels therein adapted to circulate afluid coolant therethrough.
 6. An apparatus according to claim 1 whereinsaid crucible-support rod means provides a passage for thermocouple leadwires extending into said crucible holding means.
 7. An apparatusaccording to claim 1 wherein said main furnace housing support andlifting means comprises a hydraulically operated lifting shaft attachedto said main furnace housing and means to prevent the rotation of saidshaft until it reaches said predetermined height.
 8. An apparatusaccording to claim 1 wherein said crucible holding means comprises acrucible holder terminating at its lower end in a neck member adaptedfor attachment through a collar member to said crucible-support rod, andouter shielding means surrounding said crucible holder, said crucibleholder and said outer shielding means being readily interchangeable,thereby providing means to hold crucibles of varying sizes andconfigurations.
 9. An apparatus according to claim 1 wherein saidheating means comprise rf coil means surrounding said crucible holdingmeans.
 10. An apparatus according to claim 1 wherein said heating meanscomprise resistance heater means surrounding said crucible holdingmeans.
 11. An apparatus according to claim 10 wherein said resistanceheater means comprises a graphite resistance heater, a copper pad, meansto circulate a liquid coolant in said copper pad, and means to supportsaid heater means.
 12. An apparatus according to claim 1 wherein saidheating means has leads terminating in connecting means engageable withconnecting means positioned within said furnace base member, wherebysaid heating means may be readily interchanged to accommodate differentsized crucibles.